This invention pertains to the art of timer mechanisms and more particularly to electromechanical timer mechanisms.
The invention is particularly applicable to actuating a switch within a program timer for a preselected duration. The secondary timer is set independently of the cycle selection of the main timer of a washing machine and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may be advantageously employed in a wide variety of appliances and applications.
Heretofore, timing arrangements for various household appliances have employed electromechanical timer mechanisms in an economical manner. The timer mechanisms generally utilize a cam block having plural cam tracks defined along an outer peripheral portion thereof. Cam followers are biased into abutting engagement with selected cam tracks. The cam followers are, in turn, designed to open and close electrical contact portions to provide a programmed switching action in accordance with a preselected position of the cam followers on the cam tracks. A great number of switching functions can be controlled through use of a unitary cam block. The arrangement of the cam block including its peripheral cam tracks, the cam followers, and associated switching apparatus is typically referred to as a program timer.
These program timer arrangements have met with great commercial success and are utilized in a broad cross section of appliances. Washing machines, dryers, and the like all employ timers to control various preselected programs. An operator of these appliances generally rotates the cam block to a preselected angular position corresponding to selected indicia on a control panel. For example, a ten minute permanent press cycle on a washing machine can be selected or, alternatively, a fifteen minute knit/delicate wear cycle could be chosen. Mere variation in the angular orientation of the cam block predisposes the cam tracks in a predetermined manner to open and close related electrical contact portions through the cam followers. Thus, selected angular portions of the cam block control predetermined program functions represented by the indicia on a control panel.
A drive motor rotates a cam drive which reciprocates a drive pawl. The drive pawl typically engages ratchet teeth disposed on a peripheral portion of the cam block. In this manner, the reciprocating action of the drive pawl rotates the cam block in preselected increments.
It has previously been considered unworkable to combine a secondary timing arrangement with the program timer of the cam block. Supplemental program functions can be easily accommodated on the cam block through addition of extra cam tracks and cam followers as required. These arrangements, though, are dependent on the angular starting position of the cam block and, therefore, any supplemental program functions become a part of the main program timer. Instead, an arrangement whereby the secondary timer is set and timed out. independently of the cycle selection of the main program timer is desired. Further, the secondary timer ideally would utilize the same drive mechanism that controls the main program timer without affecting its independent status.
The present invention meets the foregoing needs and others while overcoming the above-noted disadvantages in a manner that is simple, reliable, and adapted for economic use in a wide variety of applications.